The long term goal of this project is to inquire into the mechanism of the anabolic action of growth hormone (GH). Efforts will be made to study the initial metabolic events that occur in the isolated diaphragm of the hypophysectomized rat after interaction of growth hormone with its receptors. In this work, antibodies against rat growth hormone will be used to remove or neutralize growth bound to its receptors. Also, the influence of agents that modify microtubules and microfilaments will be studied. Experiments are also planned to determine whether acute fluctuations in the level of circulating growth hormone are relected in alterations in metabolic activity in the rat. The level of circulating GH will be manipulated in hypophysectomized rats bearing indwelling arterial cannulae. Effects of various levels of circulating GH on metabolism will be assessed by monitoring changes in the rate of plasma protein synthesis and in the steady-state distribution of alpha-aminoisobutyric acid.